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    <script>
        // 2、求出1-1/2 + 1/3 - 1/4 + 1/5....... 1/100的和
        
        var num = 0 
        for( var i = 1 ; i <= 100 ; i++){
            if( i % 2 !== 0 ){
                num += 1 / i
            }else if( i % 2 ===0 ){
                num -= 1 / i
            }
        }
        console.log('和为' + num)
    </script>
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